Flashing, trim & sill for through-the-wall A/C in stucco

[Woody]

I am adding an opening through my wall for an air conditioner. The exterior is Grade D paper covered by stucco. What should I use for flashing, trim, and sill? Please be as specific as possible. I'd prefer no wood exposed to the outside.

I realize I will have to break away the stucco beyond the opening itself for proper intallation of flashing. Will 4 inches beyond the opening on all sides be adequate?

Thanks!

[Tom R]

I would use 'Azek' trimboard (or similar). It's solid white PVC in 'board' form, sold at the lumber yards. If your in a newer style house, I'd probably rip it to about 2" wide for casings, older style about 3 1/2" wide. Let's say you're going with the 2". Cut your stucco back neatly in a nice straight line the 2" all the way around, but 'bevel-cut' the top at 30 degrees (upward angle). 'Bevel' the tops of both your top and bottom casings (the head and the sill) to 30 degrees. Then you'll have to also bevel the 'ends' of your side casings the same to fit. Install the bottom sill first, then the sides will 'overlap' it, then the top will 'overlap' the sides. Finish nail the casings as you go, but also use primer and PVC glue on the joints. No flashings necessary with this method. The 30 degree angles at top and bottom will shed water. If your 'stucco-cuts' are neat, use 'clear' GE silicone caulk along the outside edges of the casings. If the cuts are a little sloppy, use GE white silicone. Either way, then use white to fill the nail holes.